What controls the pore spacing in porous anodic oxides?

Overmeere, Quentin Van; Blaffart, Frédéric; Proost, Joris

doi:10.1016/j.elecom.2010.06.010

Cited by 68 publications

(79 citation statements)

References 23 publications

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“…33 Based on the oxide thickness and measured force per width at 25 V, the apparent average stress in the oxide at the completion of anodizing was −58 MPa, in good agreement with prior measurements. 22 Indeed, close agreement with the deflectometry measurements of Van Overmeere et al was demonstrated over a wide range of current densities during anodizing in phosphoric acid. 23 The current interruption was immediately followed by a nearly discontinuous increase of stress in the tensile direction.…”

Section: Resultssupporting

confidence: 74%

“…The potential and stress transients can be compared with previous measurements at similar conditions. 22,27 During the anodizing period, the cell potential increased at a rate of 0.82 V/s. Assuming an oxide density of 3.1 g/cm 3 and an electric field of 0.91 V/nm in the barrier film, the film growth rate and oxide formation efficiency are estimated to be 0.90 nm/s and 0.35, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…6,40 During barrier oxide growth in 0.4 M H 3 PO 4 , the current density obeys an exponential high-field dependence on the electric field, i = i A0 exp B E f , where E f is the electric field in the oxide, and the value of the field coefficient is B = 23.4 nm/V. 22 Accordingly, the fractional current density perturbation induced by the stress gradient would be i/i = B E f , or 230%. This large current density variation would violate charge continuity if not accompanied by a compensating space charge layer.…”

Section: Depth Distributions Of Residual Oxide Stress-mentioning

confidence: 99%

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Measurement of Stress Changes during Growth and Dissolution of Anodic Oxide Films on Aluminum

Çapraz

Shrotriya

Hebert

2014

J. Electrochem. Soc.

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While stress is thought to play an important role in the development of self-organized porous films, mechanisms of stress generation during anodizing are not yet understood. In order to reveal depth distributions of stress in anodic films, phase-shifting curvature interferometry was used to monitor force transients (in-plane stress integrated through the sample thickness) during formation of anodic oxides on aluminum in phosphoric acid, as well as subsequent open-circuit dissolution. The measurements were not influenced significantly by electrostatic stress, internal stress in the metal samples, thermal stress, or stress induced by open-circuit dissolution. At typical current densities, the force became more compressive during anodizing, while a net tensile force change was measured after anodizing followed by complete oxide dissolution. Thus, it was revealed that anodizing generates both compressive stress in the oxide and tensile stress near the metal-oxide interface. Analysis of the open-circuit stress change revealed separate contributions from diffusional stress relaxations, and removal of residual oxide stress by dissolution. Residual stress distributions in the oxide, at nanometer depth resolution, were determined from measurements of dissolution rate and stress at open circuit, and validated through variations of the open-circuit dissolution rate.

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Section: Resultssupporting

confidence: 74%

Section: Resultsmentioning

confidence: 99%

Section: Depth Distributions Of Residual Oxide Stress-mentioning

confidence: 99%

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Measurement of Stress Changes during Growth and Dissolution of Anodic Oxide Films on Aluminum

Çapraz

Shrotriya

Hebert

2014

J. Electrochem. Soc.

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“…6), stress resolution can also be improved by decreasing the substrate thickness. It should be pointed out that the substrates used in this work are over four times thicker than those in the high-resolution deflectometry measurements of Van Overmeere et al 6,23,28 This difference in substrate thickness results in almost an order of magnitude smaller curvature change for thicker substrates, assuming the same stress-thickness product of the barrier oxide film. The stability and high sensitivity of the curvature interferometer allowed accurate resolution of these curvature changes.…”

Section: Resultsmentioning

confidence: 85%

In Situ Stress Measurement During Aluminum Anodizing Using Phase-Shifting Curvature Interferometry

Çapraz

Hebert

Shrotriya

2013

J. Electrochem. Soc.

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Stress measurements yield insight into technologically relevant deformation and failure mechanisms in electrodeposition, battery reactions, corrosion and anodic oxidation. Aluminum anodizing experiments were performed to demonstrate the effectiveness of phase-shifting curvature interferometry as a new technique for high-resolution in situ stress measurement. This method uses interferometry to monitor surface curvature changes, from which stress evolution is inferred. Phase-shifting of the reflected beams enhanced measurement sensitivity, and the separation of the optical path from the electrochemical cell in the present system provided increased stability. Curvature changes as small as 10−3 km−1 were detected, at least comparable to the resolution of state-of-the-art multiple beam deflectometry. It was demonstrated that small curvature change rates of 10−3 km−1s−1 could be reliably measured, indicating that the technique can be applied to bulk samples. The dependence of the stress change during anodizing on current density (tensile at low current density, but increasingly compressive at higher current densities) was quantitatively consistent with earlier multiple-beam deflectometry measurements. The close similarity between the results of these different high-resolution measurements helps to resolve conflicting reports of anodizing-induced stress changes found in the literature.

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“…The authors found that the short-wave instability occurs in a limited range of the volume expansion, which is in agreement with 38 experimental work on the formation of ideally organized pores for a narrow range of aluminum oxide expansion. 81 Later studies 323 considered electromigration of ions in the oxide layers and showed that short-wave instabilities, which lead to hexagonal self-organization of pores, can appear even in the absence of elastic stress. Only linear stability analysis was carried out for the updated model, and it was sufficient to demonstrate transition from the basic state of the oxide (uniform compact barrier layer) to a hexagonal ordered porous structure.…”

Section: Maximizing Orderingmentioning

confidence: 99%